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Chlorophyta Homework
I. Diversity of Form Among the Chlorophyta
Examine the micrographs available on the course website showing selected genera of
green algae. For each representative genus you should determine insofar as possible the:
1. growth form
2. presence or absence of nucleus and chloroplast(s)
3. number and shape of chloroplast(s)
4. number of nuclei per cell
5. any particular wall characteristics
6. visible pigmentation
7. storage material (if possible to tell)
8. anything that can be seen of reproduction
Please don’t forget that you have Google image available to you on-line!
Volvocales
Chlamydomonas
Volvox
Coleochaetales
Coleochaete
Oedogoniolales
Oedogonium
Chlorococcales
Ankistrodesmus
Hydrodictyon
Pediastrum
Scenedesmus
II. Diversity of Form Among the Chlorophyta—Class Zygnemaphyceae
From our course website or the internet, observe and sketch these:
Chlorococcales (outgroup)
Chlorella
Zygnematales
Mougeotia
Spirogyra
Zygnema
Desmidiales
Closterium
Euastrum
Netrium
Cosmarium
Micrasterias
Staurastrum
Mesotaenium
Notes (WARNINGS!):
Sketching (biological illustration) is not only an important skill for a biologist, but is also a
potentially lucrative career path. Pasting electronic images from the internet (with citations) will
result in 50% score reduction on each image; without citations you earn course failure and
referral to judicial for plagiarism and expulsion!
If you pull out pages from this handout or add pages to this handout, you must staple the
pages of this assignment, in order and in the very-upper-left corner, before handing this
assignment in for grading. Paper clips and folded-corners are not acceptable alternatives!
(5 points deduction).
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Document © Ross E. Koning 1994. Permission granted for non-commercial instruction.
Koning, Ross E. 1994. Chlorophyta. Plant Information Website.
http://plantphys.info/plant_biology/labdoc/chlorophyta.doc
Make and label a quick sketch of the green algae micrographs to help distinguish them. Labels
are how you get points! 4 points each. Think cell structure; these are eukaryotes so they have
organelles for you to label! How are the cells organized?
Chlamydomonas
Volvox (enlarge one or a few cells also)
Coleochaete
Oedogonium
Ankistrodesmus
Scenedesmus
Pediastrum
Hydrodictyon
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Page 2
Using the website resources, make and label (cell parts, chloroplast, and any colors observed) a
quick sketch of the Zygnemaphyceae available to help distinguish them. 4 points each.
Chlorella (outgroup)
Closterium
Cosmarium
Euastrum
Mesotaenium
Micrasterias
Mougeotia
Netrium
Spirogyra
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Page 3
The Zygnemaphyceae is a
class of green algae which
demonstrates evolutionary
trends from unicellular to
filamentous organization.
Interestingly the
morphology of each cell
and the chloroplasts in the
filamentous genera are
remarkably similar to
those of the free-living
unicellular species
Staurastrum (seek additional Zygnema
views on Google Image for 3rd
dimension)
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III. Observing the Results of Evolution in the Zygnemaphyceae
Examine the diagrams you have made of each genus of Zygnemaphyceae (page 3 and
above) observed on the website (genus names need to be capitalized and italicized), and think
about the characteristics that distinguish them. Construct a dichotomous key (see examples in
Ayers Gap Field Trip Handout) using the characteristics of the ten ingroup genera you have
observed. Your key needs to be truly dichotomous (no trichotomies!) and clearly and accurately
distinguishing the genera of the ingroup! Make sure the characters are clearly described:
“spherical” (3D) is different from “discoid” (flattened sphere) or “circular.” An alga’s shape or
its chloroplast shape cannot key out as “circular” in one step and “pointed/lobed” in another step!
If your key is attached as a typed/printed item, add a title and use leader-tabs for the numbered
steps!
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Algae Vocabulary
Genome
diploid: having two sets of chromosomes, two genomes
haploid: having one set of chromosomes, a single genome
meiosis: reduction division producing haploid from diploid
syngamy: union of haploid gametes to produce diploid
Life Cycle
diplohaplontic (sporic): separate multicellular haploid and diploid phases
diplontic (gametic): spore becomes gamete; vegetative body is diploid
gametophyte: the haplophase of a diplohaplontic life cycle
haplontic (zygotic): zygote becomes sporocyte; vegetative body is haploid
sporophyte: the diplophase of a diplohaplontic life cycle
Gametes
gamete: a hapoid sexual cell which unites during syngamy with its mate
amoeboid: wall-less cells with pseudopod properties like Amoeba
anisogamous: motile gametes: small male, large female Chlamydomonas braunii
conjugation: gametic fusion without any motile phase involving lateral fusions
isogamous: motile gametes identical (+/-) Chlamydomonas reinhardtii
oogamous: motile male gamete, sessile female gamete Chlamydomonas coccifera
spermatozoid: the motile male gamete in oogamous species
heterothallic: mating types are on separate thalli
homothallic: thallus produces both mating types
antheridium: a cell producing sperm cells
oogonium: a cell producing eggs
hypnozygote: a zygotic resting cell
zygote: the diploid product of syngamy
Cell structures
phragmoplast: assembly of microtubules peripheral and parallel to the spindle
phycoplast: assembly of microtubules perpendicular to the spindle
cell plate: coalescing vesicles of wall material to form new wall between daughter cells
furrowing: a pinching off of the cell between daughters, centripetal wall growth
eyespot = stigma: an area of chloroplast loaded with carotenoid pigments just opposite the
photoreceptor
photoreceptor: a pigment, commonly rhodopsin, in cell membrane used for phototaxis
phototaxis: movement toward or away from light
chloroplasts: have the usual double outer membrane but no endoplasmic reticulum envelope. The
thylakoids are lamellate with a varying number in each granum. Thylakoids contain
chlorophylls a and b and use lutein, zeaxanthin, volaxanthin, etc. as antenna pigments.
The usual products of photosynthesis include starch ( 1,4 glucan) and oils. The
chloroplast genome consists of several circles of naked DNA
pyrenoid: an accumulation of ribulose bis phosphate carboxylase oxygenase (RuBisCO) and
often associated with starch grains
Flagella
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biflagellate: with 2 flagella
flagellum: an elongate projection from a cell with an axoneme of 9 peripheral doublet
microtubules and 2 central microtubules
heterokont: flagella different
isokont: flagella identical
quadriflagellate: with 4 flagella
stephanokont: many flagella in ring at end of cell
Forms
coccoid: unicellular non-motile cells, not always rounded
filamentous: chains of cells, branched or unbranched
flagellate: a motile cell by virtue of flagella
heteromorphic: haploid and diploid vegetative phases are morphologically different
holdfast = hapteron: a disc-like or root-like appendage involved with attachment
isomorphic: haploid and diploid vegetative phases are morphologically similar
monad: a solitary flagellate cell
palmelloid = tetrasporal: cells in clumps held inside a mucilage sheath
rhizoid: a root-like filament of cells usually involved with attachment
sarcinoid: cells in packets
siphonocladus: filament of coenocytic cells
siphonous: coenocytic cell usually with large vacuole
stolon: a creeping section of the visible part of a thallus
thallose: sheets or parenchymatous
thallus: a relatively undifferentiated plant body without leaf, stem, and roots
unicellular: single-celled uninucleate
Asexual Reproduction:
aplanospores: reproductive cells look flagellated (eyespots, contractile vac) but are not
autospores: non-motile asexual reproductive cells, like vegetative cell
coenobium: endospores form colony and are released as a unit
planospores: a motile zoospore
zoospore: a flagellated spore
Habit
Benthic: living attached to a substrate
Epilithic: living attached to a rock
Epiphytic: living attached to a plant
Epizoic: living attached to an animal
Eutrophic: waters with excessive nutrients
Oligotrophic: waters with depleted nutrients
Pelagic: floating at or near the water's surface
Planktonic: living freely suspended in water
Producer: involved in primary production = photosynthesis
Terrestrial: living on land
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Division Chlorophyta Taxonomy: 500 genera, 8000 species!
Class Chlorophyceae
Order Volvocales: unicellular/colonial
Order Chlorococcales: coccoid
Order Chaetophorales: branching filaments
Order Oedogoniales: branched/unbranched weird sex
Class Ulvophyceae
Order Codiolales unbranched filaments
Order Ulvales: thallose
Class Cladophorophyceae
Order Cladophorales, Siphonocladales, Acrosiphonales: siphonocladous
Class Bryopsidophyceae
Order Bryopsidales: siphonous
Order Halimedales: thalloid
Class Dasycladophyceae
Order Dasycladales: siphonous
Class Trentepohliophyceae
Order Trentepohliales: branched filaments
Class Zygnematophyceae
Order: Zygnematales: coccoid to unbranched filaments, special cytology
Order Desmidiales: unicellular with semicells
Class Klebsormidiophyceae
Order Klebsormidiales: sarcinoid, filamentous
Order Coleochaetales: pseudoparenchymatous
Class Charophyceae
Order Charales: unique vegetative structure and reproduction
Further notes on constructing a key:
The first dichotomous step of a key, should use a particular feature divide the ingroup
into two major subgroups. For this key there is a huge hint on page 1!
The first part of this dichotomy (1a) should refer the one subgroup to step 2, which will
then use dichotomies 2 through n to distinguish the members of this one subgroup.
The second part of this dichotomy (1b) should refer the other subgroup to step n+1, which
will then use dichotomies n+1 through n+x to distinguish the members of this second subgroup.
After drafting it, be sure to test your key to be sure that it actually works to
unambiguously and accurately distinguish and identify each of your ingroup species!
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